1. Field of the Invention
This invention relates to the field of battery charging devices.
2. Description of the Related Art
A battery charging device is a device used to charge and recharge one or more rechargeable batteries. A battery is a device that consists of one or more cells (a cell is a device that converts a store of chemical energy into electrical energy) that are connected to act as a source of electric power. A rechargeable battery is a device whose one or more cells can be substantially reenergized once the store of chemical energy in the rechargeable battery has been partially or completely depleted.
A variety of electronic devices utilize rechargeable batteries (e.g., portable computers, portable computer peripherals, personal digital assistants (PDAs), cellular phones, and cameras). Different electronic devices often have different power usage profiles (e.g., a camera will typically have a power usage profile different from a portable computer). The same electronic devices will often have different power usage profiles dependent upon the modes of usage (e.g., a portable computer frequently accessing its hard-disk drive access typically has a significantly different power usage profile from the same portable computer which is instead accessing its Random Access Memory (RAM) rather than its hard-disk drive). These differing power usage profiles often create different size, shape, weight, and electrical loading requirements on the rechargeable batteries being used by the devices.
Because of the wide variety of power usage profiles of the devices which utilize rechargeable batteries, a number of different rechargeable battery chemistries (e.g., nickel cadmium (NiCd), nickel-metal hydride (NiMH), lithium ion (Li-ion) and lithium-polymer (Li-polymer)) have been developed, each having certain advantages and disadvantages. In general, the different rechargeable battery chemistries have been developed to provide the optimum of battery power on the basis of certain user-ranked criteria (e.g., cost, constant power drain versus "surge" or "spiked" power drain, time to recharge, total number of possible rechargings, etc.).
The use of different rechargeable battery chemistries often allow modern rechargeable batteries to provide power to their respective devices for times far in excess of rechargeable batteries used in the past. However, it is still common for user requirements to exceed battery life. For example, even the most optimum batteries utilized in modern portable computers typically provide only a useable battery life of somewhere in the neighborhood of 3 hours, with the more common cheaper batteries typically providing between 1 and 1.5 hours of useable battery life. Consequently, it is common for users to carry with them "back up" or "spare batteries" with which to replace a battery when its power is expended, especially when it is likely that a long work-session is likely (i.e., one that will extend far beyond three hours).
At the end of a long work-session, it is not uncommon for a user to have several expended batteries. Since most modern portable devices (such as portable computers) have internal battery charging circuitry, it is possible to charge at least one of these expended batteries by connecting the portable device to an AC power source. However, most users prefer to charge all batteries (i.e., more than one) simultaneously. This is typically done with the use of external battery chargers.
FIG. 1 illustrates a typical multi-battery charging scenario as it typically exists in the current art. Shown is portable computer 100. Portable computer 100 may, through DC output connector 101 and its associated cabling, be connected to AC adapter 102, which is in turn connected to AC power outlet 106. Battery pack 104 is also shown which resides within computer 100. AC adapter 102 converts AC power into DC power that can be used to power computer 100 and charge the battery pack 104.
Further shown is external battery charger 120. Depicted is external battery charger base unit 110. External battery charger base unit 110 is connected to AC adapter 112 which is in turn connected to AC power outlet 106. Battery pack 108 is also shown which resides within battery slot receptor 116 within external battery charger base unit 110. AC adapter 112 converts AC power into DC power that can be used to charge battery pack 108.
External battery charger base unit 110 is formed to receive battery pack 108. Furthermore, as was mentioned above, several different battery chemistries are now being utilized within the industry. In order to extract optimum use and life from the batteries, it is necessary to charge the batteries in the fashion most compatible with the battery chemistries. Consequently, it is common for external battery charger base unit 110 to contain charging circuitry optimized for a particular battery chemistry. Furthermore, battery slot receptor 116 also contains a battery connector (not shown) appropriate to the battery to be charged (usually the connector and charging circuitry are vendor specific, and one vendor'external charger cannot be used with another vendor'batteries; furthermore, it is usual for the charger to only be rated as safe to charge one particular type of battery chemistry).
As can be seen in FIG. 1, external battery charger 120 takes up a considerable amount of space. Furthermore, each component has a considerable amount of weight. Since battery powered devices are typically utilized to provide portability and are often transported to remote locations, external battery charger 120 must also be so transported if the ability to simultaneously recharge a number of back-up batteries is desired. Furthermore, since under the current art battery chargers are typically optimized for one particular type of battery chemistry, it is necessary to carry multiple different types of external battery chargers 120, or at the least, external battery charger base units 100, should the use of various different battery chemistries be desired.
It is apparent that external battery chargers are very useful, and that irrespective of advances in battery technology, it is likely that such a need will persist in the future. As has been discussed, current external battery chargers have considerable bulk and weight, and are typically optimized for only one type of battery chemistry. In light of the foregoing, it is therefore apparent that a need exists in the art for a method and apparatus which provide external battery chargers of considerably less bulk and weight than those currently available, and which will also serve as a universal charger across various different battery chemistries.